APPROACH TO THE PATIENT WITH SUSPECTED OR CONFIRMED ARRHYTHMIAS



History-taking in patients with suspected or confirmed rhythm abnormalities should be aimed at detecting tbe presence of cardiac or noncardiac disease that may be linked causally to the genesis of a rhythm abnormality. Common symptoms that prompt patients with rhythm disturbances to con­sult a physician are palpitations, syncope, pre-syncope, and congestive heart failure. The ability of a patient to sense an irregular, slow, or rapid heart rhythm varies greatly; some patients are completely unaware of a marked arrhythmia whereas others feel every premature impulse. In addition, some patients may complain of palpi­tations when they have no detectable rhythm dis­turbance or merely sinus tachycardia. Dizziness is a common complaint in people with tachy- or bradyarrhythmias but also may be due to nonar-rhythmic causes. Syncope refers to complete but transient loss of consciousness and also has a va­riety of causes (see Table 8-9). Exacerbation of congestive heart failure may occur with arrhyth­mias. If a patient senses palpitations, the physi­cian should determine whether the patient senses a slow heart beat, a rapid heart beat, a regular or irregular heart beat, its rate, and whether the onset and termination of the palpitations are sudden or gradual.

The physical examination is useful to detect ev­idence of underlying cardiac disease. In addition,abnormalities of the pulse may be noted, and clues regarding AV dissociation during an ar­rhythmia may be detected (for example, inter­mittent cannon a waves in the jugular venous pulse or varying intensity of Si during a regular tachyarrhythmia).

The resting electrocardiogram may reveal the specific arrhythmia responsible for symptoms or give clues regarding a tachyarrhythmia; for ex­ample, short episodes of nonsustained ventricular tachycardia may be recorded in a patient who has presented with syncope or cardiac arrest due to a sustained ventricular tachycardia. In addition, in­direct evidence may be obtained from the elec­trocardiogram that may suggest the etiology of the arrhythmia; for example, the presence of a delta wave should alert the physician to the possibility that a tachycardia due to Wolff-Parkinson-White syndrome may be present. The electrocardiogram may also provide evidence as to the etiology of the arrhythmia, such as the presence of ischemic heart disease documented by ECG evidence of my­ocardial infarction.

Long-term ambulatory electrocardiography (Holter monitoring) is an important tool for eval­uating patients with suspected arrhythmias. It permits quantitation of arrhythmia frequency and complexity, correlation with the patient’s symp­toms, potential diagnosis of an unknown arrhyth­mia, and evaluation of the effect of antiarrhythmic therapy. It can record arrhythmias while patients are engaged in their normal daily activities. It can also document alterations in the QRS, ST, and T waves and may be useful in documenting pace­maker function or malfunction. Certain arrhyth­mias are common during prolonged ECG moni­toring in normal patients and may be of no clinical significance. In many patients symptoms are very infrequent and difficult to detect even with pro­longed electrocardiographic monitoring. Exercise testing can be used to precipitate arrhythmias in some patients. Patients with no demonstrable structural heart disease may have an increase in premature ventricular or atrial complexes with exercise. However, patients who have ischemic heart disease are more likely to have ventricular ectopy at lower heart rates and in the early re­covery period.

Invasive electrophysiological procedures are useful and involve introducing catheter elec­trodes into the heart to record electrical activity from the atria, ventricles, and the His bundle, and to stimulate the atria or ventricles electrically. Su­praventricular or ventricular tachycardias may be induced by programmed electrical stimulation. The test may be used diagnostically to determine whether a particular rhythm disorder exists or to determine the mechanism of a known arrhythmia. The test may also be used therapeutically to ter­minate a tachycardia or to determine the efficacy of drug or other therapy. Electrophysiological test­ing is important in patients with resistant tachy­arrhythmias undergoing either surgical resection or ablation of a tachycardia focus or accessory pathway. Patients considered candidates for an-titachycardia pacemaker devices or implantable cardioverter-defibrillator devices require electro­physiological study to confirm the mechanism and origin of the arrhythmia and the efficacy and safety of this mode of therapy. Electrophysio­logical study may be helpful in identifying pa­tients with sinus nodal dysfunction or atrioven­tricular block.
Esophageal electrocardiography is sometimes a useful noninvasive technique to diagnose ar­rhythmias. An electrode introduced approxi­mately 40 cm from the patient’s nares into the esophagus can record an atrial electrogram and often can be used to pace the atrium.

Autonomic and pharmacological manipula­tions sometimes aid in diagnosing arrhythmias. Most commonly, vagal maneuvers (e.g., carotid sinus massage), edrophonium, or administration of verapamil to slow AV nodal conduction are used. Carotid sinus massage is performed with the patient in the supine position. With the neck hy-perextended and the head turned away from the side being tested, light pressure is applied to the carotid impulse at the angle of the jaw. If no change occurs, pressure is more firmly applied with a gentle rotating motion for approximately 5 seconds on one side and then on the other; both sides are not stimulated simultaneously. Prior to carotid sinus massage, the carotid artery should be auscultated; massage should not be performed in patients who have carotid bruits.